1. Field of Invention
The present invention relates to an optical pick-up device comprising a plurality of light sources and a common optical system for guiding lights emitted from the light sources to an optical recording medium in order to reproduce different optical recording media such as a CD or a DVD or carry out recording and reproduction.
2. Related Art
There has been known an optical pick-up device of a plural light source type which is incorporated in an interchangeable optical type information reproducing device capable of reproducing a DVD, CD, CD-R, CD-R/RW (which will be hereinafter referred to as CDs). For example, one of the present applicants has proposed an optical pick-up device comprising two laser diodes for emitting laser beams having different wavelengths to reproduce a DVD and a CD which have different thicknesses.
Such an optical pick-up device of a 2-light source type comprises a laser diode for emitting a laser beam for a CD having a wavelength of 780 nm and a laser diode for emitting a laser beam for a DVD having a wavelength of 650 nm, for example, and is constituted to receive a return light from an optical recording medium to one common light receiving element, thereby generating a reproducing signal and a servo signal for correcting a tracking error and a focusing error.
The two laser diodes and the light receiving element are positioned in the following manner to have an optical conjugating relationship with each other. First of all, one of the laser diodes is fixed to an attachment portion which is formed on a device frame (head base) in advance. Next, a position of the light receiving element is adjusted in a direction of an optical axis and a direction of a plane orthogonal to the optical axis such that the light receiving element is set in a conjugating position with the laser diode, and the light receiving element is attached to the device frame after the adjustment. Then, positions of the other laser diode in x, y and z directions are adjusted such that the laser diode is set in a conjugating position with the laser diode and the light receiving element which have already been fixed, and the laser diode is thus bonded and fixed to the device frame. In general, the other laser diode is holding a hold. And the holder and the device frame is bonded and fixed in y direction of the device frame contacting the holder.
In the optical pick-up device of a 2-light source type for reproduction, generally, an optical system for DVD reproduction requires higher positioning precision than an optical system for CD reproduction. Therefore, the laser diode for DVD reproduction is set to be a fixation side laser diode to be fixed to the attachment portion formed on the device frame, and the laser diode for CD reproduction is set to be an adjustment side laser diode to be bonded and fixed to the device frame after the positional adjustment in x, y and z directions.
The adjustment side laser diode is held in a holder having a smaller heat capacity than that of the device frame, and the holder is chucked by means of a positioning jig to adjust the position of the adjustment side laser diode, and is bonded and fixed to the device frame after the adjustment.
Thus, the adjustment side laser diode is held in the holder having a smaller heat capacity, and furthermore, the holder is fixed to the device frame side with an adhesive having poor heat radiation. Accordingly, the adjustment side laser diode has poorer heat radiation than that of the fixation side laser diode fixed to the attachment portion formed on the device frame.
In the optical pick-up device dedicated to reproduction, the adjustment side laser diode has a small calorific value. Therefore, the heat radiation of the adjustment side laser diode has no particular problem. However, in an optical pick-up device for recording, a laser diode to be used has higher output power than that of the optical pick-up device dedicated to reproduction. Consequently, a calorific value is also increased. Thus, there is a possibility that the laser diode might be overheated to an allowable temperature or more through self heat generation in a real use state.
Furthermore, the other laser diode is holding a hold. And the holder and the device frame are bonded and fixed in the y direction of the device frame contacting the holder. So, a strain is caused in the x direction.
However, in the optical pick-up device comprising a plurality of light sources, the heat generation of each light source and bad effects caused thereby have not conventionally been considered. Under the actual circumstances, accordingly, the countermeasures have not been proposed.
Therefore, it is an object of the invention to provide an optical pick-up device comprising a plurality of light sources, each of which is never brought into an overheating state, and a method of manufacturing the optical pick-up device.
In order to solve the above-mentioned problems, the invention provides an optical pick-up device comprising first and second light sources, an attachment portion having the first light source attached thereto being formed on a device frame or the first light source being attached to a light source holder and the light source holder being provided in close contact with the device frame, the device having a light source holder holding the second light source and fixed to the device frame, and a common optical system for guiding lights emitted from the first and second light sources to an optical recording medium, wherein a calorific value of the first light source in a real use state is greater than that of the second light source in the real use state.
In the invention, the first light source having a great calorific value is attached to the device frame side having a great heat capacity and high heat radiation, and the second light source having a small calorific value is attached to the light source holder side. Therefore, it is possible to prevent each light source from being brought into an overheating state.
In order to improve the precision and reliability of the fixing position of the light source holder holding the second light source, it is desirable that a clearance should be formed between the light source holder holding the second light source and the device frame and the light source holder should be bonded and fixed to the device frame with an adhesive partially filled in the clearance.
Furthermore, it is desirable that the adhesive should bond and fix the light source holder to the device frame such that a main volume thereof is included in a space in which they are opposed to each other.
In general, a light source for recording having great output power is used for the first light source and a light source for reproduction having small output power is used for the second light source.
As an example, the first light source is a laser beam source for CD-R/RW recording and the second light source is a laser beam source for DVD reproduction.
The invention provides an optical pick-up device comprising first and second light sources, an attachment portion having the first light source attached thereto being formed on a device frame or the first light source being attached to a light source holder and the light source holder being provided in close contact with the device frame, the device having a light source holder holding the second light source and fixed to the device frame, and a common optical system for guiding lights emitted from the first and second light sources to an optical recording medium, wherein a calorific value of the first light source in a real use state is greater than that of the second light source in the real use state, and a method of manufacturing the optical pick-up device in which a clearance is formed between the light source holder holding the second light source and the device frame and the light source holder is bonded and fixed to the device frame with an adhesive partially filled in the clearance.
In the method according to the invention, first of all, the light source holder holding the second light source is positioned such that the second light source has a conjugating positional relationship with the first light source with respect to the common optical system in a state in which the first light source is attached to the light source attachment portion. Next, the adhesive is partially filled between the light source holder and the device frame to bond and fix the light source holder to the device frame.
In the method according to the invention, the positioning is carried out in a state in which the light source holder is provided apart from the device frame, that is, it floats. Therefore, the positioning can be carried out more easily with higher precision as compared with the case in which the positioning is performed along the side surface of the device frame.